Get the DEF property of a x3d node
Found the problem: In Blender 2.74, inside

def getDefName(self):
        data = self.x3dNode.getAttributeNode('DEF')
        if data:
            data.value  # XXX, return??
        return None


Does not return the name in case it found it, changing it to 

def getDefName(self):
        data = self.x3dNode.getAttributeNode('DEF')
        if data:
            return data.value  # XXX, return??
        return None


worked for me, however I don't know how to suggest it as a bug fix nor am I sure that it is indeed a worthy fix as clearly someone already noticed that this function doesn't return anything in case there is a DEF.